World number one Novak Djokovic was handed a blockbuster Olympics opener on Thursday when he was drawn to face Juan Martin del Potro, who beat him for bronze at London in 2012.
Djokovic, whose best performance was a bronze medal at the Beijing Games in 2008, is the top seed at the tournament which gets underway on Saturday.
The Serb has an 11-3 record against the giant Argentine, although the two have not met for three years.
Djokovic, seeking to complete a Golden Slam of all four majors and Olympic gold, took revenge for his shattering loss at the London Games with a titanic five-set win in the Wimbledon semi-finals in 2013.
Del Potro, the 2009 US Open champion, comes into Rio with a world ranking of 145 having been as high as four in 2011 before his career was almost ended by four wrist operations.
Second seed and defending champion Andy Murray begins against Serbia's Viktor Troicki.
Wimbledon champion Murray boasts a 7-0 record against Troicki, the world 45.
The British star, who will carry his country's flag at Friday's opening ceremony, has not dropped a set against the Serb since 2011 when he came back from two sets down to win their fourth round French Open clash.
Third seeded Rafael Nadal, the 2008 champion, faces Federico Delbonis of Argentina, the world number 43.
Nadal missed the London Olympics with a knee injury and like Murray will have flag-bearing duties on Friday.
The 30-year-old has a 2-0 career lead over Delbonis but has come into Rio having not played since a left wrist injury forced an early withdrawal from the French Open in May.
Nadal intends to play all three events in Rio -- singles, men's doubles with Marc Lopez and mixed with French Open champion Garbine Muguruza.
Japanese fourth seed Kei Nishikori, runner-up to Djokovic in Toronto at the weekend, starts against Albert Ramos of Spain, whom he has never met before.
Nishikori was a quarter-finalist at the London Games in 2012.
- 'Very strong draw' -
In the women's draw, defending champion and world number one Serena Williams will open against Australia's Daria Gavrilova.
The 34-year-old American already has a singles gold from London four years ago as well as three doubles titles with sister Venus, who is also in the Rio event.
Williams hasn't played since lifting a seventh Wimbledon title in July which allowed her to equal Steffi Graf's Open era record of 22 majors.
She beat Russian-born Gavrilova in straight sets in their only previous meeting in Doha in 2013. Sister Venus could be a semi-final opponent.
Australian Open champion and second seed Angelique Kerber starts against Mariana Duque Marino of Colombia.
Third seed Muguruza begins against Serb veteran Jelana Jankovic while fourth seeded Agnieszka Radwanska of Poland faces China's Zheng Saisai.
The Rio tennis tournament has suffered a host of high-profile pull-outs, a factor that International Tennis Federation (ITF) president David Haggerty insists has not watered down the quality.
"The Olympics is different from other events and the draw is very strong," Haggerty told AFP.
"We are proud of the people here. Everyone has to make a decision on whether to take part based on personal and family conditions.
"But I think that some of the players not here may well think back in later life, 'gee, I wish I had taken that opportunity'."
Top 10 players Roger Federer, Stan Wawrinka, Milos Raonic, Tomas Berdych and Dominic Thiem are not playing in Rio.
The women's event is without Simona Halep, Victoria Azarenka, Belinda Bencic and the banned Maria Sharapova.